Bakersfield Night Sky – March 5, 2016
By Nick Strobel
A couple of news items about exoplanet research show clearly that astronomers, impatient to get results sooner than later, are extending the reach of current telescopes instead of waiting for big, new telescopes to come online. Both of these stories involve the Hubble Space Telescope but similar sorts of advances happen with existing ground-based telescopes as well. The first is about the super-Jupiter orbiting the brown dwarf 2M1207 (the "2M" refers to the 2MASS infrared survey and the "1207" refers to its celestial coordinates on the sky). Discovered over a decade ago, the super-Jupiter, 2M1207b, is the first directly-imaged exoplanet and also the first one discovered orbiting a brown dwarf, a failed star that is a transition object between a really big jovian planet and a small star.
Rather than wait for the James Webb Space Telescope to point its infrared eye toward the exoplanet, astronomers used the Hubble Space Telescope's Wide Field Camera 3 to measure the rotation rate of the exoplanet by observing how the brightness of the exoplanet changed in the infrared. The Webb won't launch until 2018, so astronomers wanted to see if they could push Hubble's camera to make the measurement. It helps that 2M1207b glows quite brightly in the infrared because it is only 10 million years old and still warm from its formation. Temperatures in its atmosphere are about 2200 to 2600 deg Fahrenheit, so toasty warm that its upper-level clouds are made of silicate droplets and lower-level clouds are made of iron droplets. It is the motion of those clouds that astronomers are able to detect and measure the exoplanet's rotation rate: approximately 10 hours. That's as fast as Jupiter spins. Webb will enable us to better determine the 2M1207b's atmospheric composition along with that for plenty of other exoplanets but the technique was developed with Hubble. 2M1207 is about 170 light years away.
Four times closer is the planetary system 55 Cancri at just 40 light years away. One of the exoplanets in the system is a super-Earth that orbits so close to its star, it takes less than 24 hours to orbit the star and its temperature is a very hot 3100 deg F. The exoplanet, "55 Cancri e", is about twice the diameter of the Earth (hence the "super-Earth" label) and has eight times the Earth's mass.
This hot dense world is thought to be made mostly of carbon compounds instead of silicate minerals like the Earth because of its extreme heat. Astronomers used Hubble's Wide Field Camera 3 to create a spectrum of 55 Cancri e's atmosphere. No easy task, this is the first successful measurement of a super-Earth's atmospheric composition. The atmosphere is made mostly of hydrogen and helium and possibly hints of hydrogen cyanide, a molecule that would be found in abundance only in a carbon-rich environment, not a silicate-rich environment. The Webb will give us a clearer, more distinct spectrum, of course but astronomers are going to push the abilities of current telescopes and analysis techniques to make discoveries before Webb comes online.
Later this month, the ESA ExoMars Trace Gas Orbiter and Schiaparelli mission should launch. The launch window is March 14th through 25th when Mars and Earth are properly positioned for an energy-efficient trip. The ExoMars mission will arrive at Mars in mid-October. The Trace Gas Orbiter will be looking for gases that could be produced by biological processes, particularly methane and its degradation products. However, since methane can also be produced through geological processes, it won't prove that martian life exists if it finds methane. The Trace Gas Orbit will also look for water vapor, nitrogen oxides and acetylene with an improved accuracy of a thousand times better than has been done before.
Schiaparelli is a short-lived lander that will be a testbed for various controlled landing systems. These entry, descent, and landing systems will be used on future landers launched by the European Space Agency (ESA). In 2018, ESA hopes to land a rover on Mars that will carry a drill and a suite of instruments for exobiology and geochemistry research. Here on Earth, researchers are developing techniques and instruments to detect life in Mars-like conditions in the driest part of the Atacama desert, already the "driest place on Earth." NASA's Atacama Rover Astrobiology Drilling Studies (ARADS) project just finished its first month-long session at the end of February. Although much warmer than Mars, the extreme dryness and ultraviolet exposure due to its high elevation, the Atacama desert provides a Mars-like laboratory for studying the limits of life and testing life-detection technologies.
In Bakersfield's sky, the evening display is now quite nice with Orion and Canis Major up high in the southwest sky (see the first star chart below). The belt of Orion points left to the brightest star of the night sky, Sirius, just 8.6 light years away. Sirius is white hot, almost twice as hot as the Sun and it puts out 26 times more energy. Circling Sirius is a very faint white dwarf over twice as hot as Sirius but nearly 10,000 times dimmer due to its small size, only 0.92 times the diameter of the Earth. The white dwarf was once a blazing bright star even brighter and hotter than Sirius but since it was once more massive than Sirius, it went through its hydrogen store faster than Sirius is doing now.
As the Sun is setting, you'll see Jupiter rising. Jupiter will be at "opposition", or opposite the Sun, on March 8th. Even brighter than Sirius, you'll see Jupiter below the tail end of Leo for the next several months as it moves retrograde until early May and then resumes drifting eastward below Leo. Shortly after midnight, you may be able to spot orange-red Mars among the dim stars of Libra. About an hour later, Saturn will become visible between Scorpius and Ophiuchus.
Early risers may be able to spot a very thin Waning Crescent Moon to the upper right of Venus and then just left of Venus the following morning (see the second star chart below) but it will be difficult to spot both of them since they are now so close to the Sun on our sky.
Want to see more of the stars at night and save energy? Shield your lights so that the light only goes down toward the ground. See www.darksky.org for how.
Director of the William M Thomas Planetarium at Bakersfield College
Author of the award-winning website www.astronomynotes.com